System and method for analyzing noise

ABSTRACT

A system and method for analyzing noise includes an error information storage unit storing threshold values of malfunction factors that create a malfunction of a victim receiver cell due to a noise, an error criterion generation section which selects the threshold values from the error information storage unit, and generates an error criterion according to the victim receiver cell by plotting the threshold values and conducting the threshold values smooth processing on, a noise analysis section configured to measure the malfunction factors, and a comparison section configured to compare the measured malfunction factors to the error criterion, and to judge whether the noise will create a malfunction of the victim receiver cell when the malfunction factors meet the error criterion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Applications No. P2003-176643, filed on Jun.20, 2003; the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to technology for analyzing noise of anintegrated circuit by use of a computer, and specifically relates to anoise analysis system and a noise analysis method to analyze crosstalknoise generated in wires of the integrated circuit.

2. Description of the Related Art

In an integrated circuit, since a transistor with low output impedancehas a large driving capability, the waveform of a signal transmittedfrom such a transistor tends to generate significant crosstalk noise ina signal propagated through an adjacent wire. On the contrary, since atransistor with high output impedance has a low driving capability, thewaveform of a signal transmitted from such a transistor is subject tothe influence of crosstalk noise. With increased integrated circuitdensity, the crosstalk noise, which causes a malfunction of a logiccircuit, has been a significant problem.

In a conventional crosstalk noise analysis method, a criterion forjudging or determining generation of crosstalk noise is whether thecrosstalk noise inverts the logic of a receiver cell in a state where aconstant signal (high or low signal) is being propagated (hereinafter,referred to as “a static state”) through a wire.

However, the conventional crosstalk noise analysis method does not takeinto consideration the influence of crosstalk noise in a state where arising or falling signal is being propagated (hereinafter, referred toas “a transition state”). In some cases, crosstalk noise does not causea malfunction of the receiver cell in the static state while crosstalknoise is generated in a rising or falling signal propagated through thewire and causes a malfunction of the receiver cell in the transitionstate. Therefore, the conventional crosstalk noise analysis methodcannot completely prevent a malfunction of the receiver cell. In thisspecification, the “rising signal” and “falling signal” is not limitedto rising and falling sections of a rectangular wave signal such as theleading and trailing edges of a clock pulse, but also represent therising and falling signals propagating in wires, respectively.

It is also possible to equally estimate the influence of crosstalk noisein the transition state using the crosstalk noise in the static state asthe criterion to change the design. However, such design change leads toa large circuit design, thus increasing the circuit area and powerdissipation and reducing speed of the circuit.

SUMMARY OF THE INVENTION

An aspect of the present invention inheres in a system for analyzingnoise including an error information storage unit storing thresholdvalues of malfunction factors that create a malfunction of a victimreceiver cell due to a noise, an error criterion generation sectionwhich selects the threshold values from the error information storageunit and generates an error criterion according to the victim receivercell by plotting the threshold values and conducting the thresholdvalues smooth processing on, a noise analysis section configured tomeasure the malfunction factors and a comparison section configured tocompare the measured malfunction factors to the error criterion, and tojudge whether the noise will create a malfunction of the victim receivercell when the malfunction factors meet the error criterion.

Another aspect of the present invention inheres in a computerimplemented method for analyzing noise including generating an errorcriterion according to the victim receiver cell by plotting thethreshold values and conducting the threshold values to smoothprocessing on, measuring the malfunction factors, comparing the measuredmalfunction factors to the error criterion and judging whether the noisecreates a malfunction of the victim receiver cell when the malfunctionfactors meet the error criterion.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view schematically showing a system for analyzing noise of afirst embodiment of the present invention.

FIG. 2 is a view schematically showing the circuit wherein crosstalknoise is generated.

FIG. 3 is a waveform chart schematically showing crosstalk noisegenerated in a rising signal.

FIG. 4 is a waveform chart schematically showing crosstalk noisegenerated in a falling signal.

FIG. 5 is a graph schematically showing a combinational error criterionof noise voltage in a falling signal and noise duration in the fallingsignal.

FIG. 6 is flow diagram schematically showing a method for analyzingnoise of the first embodiment of the present invention.

FIG. 7 is a view schematically showing a system for analyzing noise of asecond embodiment of the present invention.

FIG. 8 is a graph schematically showing a combinational error criterionof noise voltage in a falling signal, noise duration in the fallingsignal, and victim receiver cell load capacity.

FIG. 9 is flow diagram schematically showing a method for analyzingnoise of the second embodiment of the present invention.

FIG. 10 is a view schematically showing a system for analyzing noise ofa third embodiment of the present invention.

FIG. 11 is waveform chart schematically showing rinsing crosstalk noisein a constant signal.

FIG. 12 is waveform chart schematically showing falling crosstalk noisein a constant signal.

FIG. 13 is a graph schematically showing a combinational error criterionof rising noise voltage and rising noise duration in a constant signal.

FIG. 14 is flow diagram schematically showing a method for analyzingnoise of the third embodiment of the present invention.

FIG. 15 is a view schematically showing a system for analyzing noise ofa fourth embodiment of the present invention.

FIG. 16 is a graph schematically showing that a combinational errorcriterion of rising noise voltage and rising noise duration in aconstant signal is above a combinational error criterion of noisevoltage and noise duration in a falling signal.

FIG. 17 is a flow chart schematically showing a method for analyzingnoise of the forth embodiment of the present invention.

FIG. 18 is a view schematically showing a system for analyzing noise ofa fifth embodiment of the present invention.

FIG. 19 is a diagram schematically showing a circuit which logic istraced backward from a victim cell.

FIG. 20 is a flow chart schematically showing a method for analyzingnoise of the fifth embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Various embodiments of the present invention will be described withreference to the accompanying drawings. It is to be noted that the sameor similar reference numerals are applied to the same or similar partsand elements throughout the drawings, and the description of the same orsimilar parts and elements will be omitted or simplified.

In the following descriptions, numerous specific details are set forthsuch as specific signal values, etc. to provide a thorough understandingof the present invention. However, it will be obvious to those skilledin the art that the present invention may be practiced without suchspecific details.

(First Embodiment)

As shown in FIG. 1, a crosstalk noise analysis system according to afirst embodiment of the present invention includes a logic connectioninformation input unit 1, a CPU 2, an error information storage unit 3,a main memory unit 4, and an output unit 5, which are connected to a bus50. The CPU 2 includes an error criterion generation section 10, asimulation executing section 15, a noise analysis section 20, and acomparison section 25.

The logic connection information input unit 1 transmits data to the mainmemory 4 of a layout pattern of a logic circuit to be designed. Forexample, the logic connection information input unit 1 transmits data ofa layout pattern of a logic circuit, which is composed of a receivercell R1, a driver D2 which transmits a clock signal to the receiver cellR1 through a wire N2, a wire N1 adjacent to the wire N2, and a driver D1which transmits a general signal through the wire N1 as shown in FIG. 2.

In this specification, the driver D1 which provides the influence ofcrosstalk noise is defined as an “aggressor wire driver,” the driver D2which receives the influence of crosstalk noise is a “victim wiredriver,” the wire N1 which provides the influence of crosstalk noise isan “aggressor wire,” the wire N2 which receives the influence ofcrosstalk noise is a “victim wire,” and the receiver cell R1 whichreceives the influence of crosstalk noise is a “victim receiver cell.”

The error information storage unit 3 stores a plurality of errorinformation. The “a plurality of error information” are threshold valuesof “malfunction factors,” which cause a malfunction of the victimreceiver cell due to the crosstalk noise. The “error information,” whichis measured by a circuit simulation or an actual measurement, is storedin the error information storage unit 3. In the crosstalk noise analysissystem according to the first embodiment of the present invention, asshown in FIG. 1, noise voltage in a rising signal is stored in a firstvoltage data storage 31, noise duration in a rising signal is stored ina first duration data storage 32, noise voltage in a falling signal isstored in a second voltage data storage 33, and noise duration in afalling signal is stored in a second duration data storage 34.

The “noise voltage in a rising signal” is voltage of crosstalk noisegenerated in the rising signal propagated through a wire and causes amalfunction of the victim receiver cell. For example, as shown in FIG.3, with the falling of a signal W1 at a time T1 in the wire N1 of FIG.2, crosstalk noise is generated in the rising signal W2 propagatedthrough the wire N2 of FIG. 2, and voltage (

v=V2−V1) of the crosstalk noise causes a malfunction of the receivercell R1 of FIG. 2. In this case, the “noise voltage in a rising signal (

v)” is stored in the first voltage data storage 31 as the errorinformation.

The “noise duration in a rising signal” is the duration of crosstalknoise generated in the rising signal propagated through a wire whichcauses a malfunction of the victim receiver cell. For example, as shownin FIG. 3, with the falling of the signal W1 in the wire N1 of FIG. 2during the period of the time T1 to the time T2, the crosstalk noise isgenerated in the rising signal W2 propagated through the wire N2, andduration (

t=T2−T1) of the crosstalk noise causes a malfunction of the receivercell R1. In this case, the “noise duration in a rising signal (

t)” is stored in the first duration data storage 32 as the errorinformation.

The “noise voltage in a falling signal” is voltage of crosstalk noisegenerated in the falling signal propagated through a wire and causes amalfunction of the victim receiver cell. For example, as shown in FIG.4, with the rising of a signal W1 in the wire N1 of FIG. 2 at a time T1,crosstalk noise is generated in the falling signal W2 propagated throughthe wire N2, and voltage (

v=V4−V3) of the crosstalk noise causes a malfunction of the receivercell R1. In this case, the “noise voltage in a falling signal (

v)” is stored in the second voltage data storage 33 as the errorinformation.

The “noise duration in a falling signal” is the duration of crosstalknoise generated in the falling signal propagated through a wire andcauses a malfunction of the victim receiver cell. For example, as shownin FIG. 4, with the rising of the signal W1 in the wire N1 of FIG. 2during the period of the time T3 to the time T4, the crosstalk noise isgenerated in the rising signal W2 transmitted through the wire N2, andthe duration (

t=T4−T3) of the crosstalk noise causes a malfunction of the receivercell R1. In this case, the “noise duration in a falling signal (

t)” is stored in the second duration data storage 34 as the errorinformation.

The error information varies depending on the type and characteristicsof the victim receiver cell. Accordingly, the error information storageunit 3 stores a plurality of error information which varies depending onthe type and characteristics of the victim receiver cell.

The main memory unit 4 stores the layout pattern supplied as data by thelogic connection information input unit 1 and data processed by the CPU2. The output unit 5 transmits a part of the layout pattern at which itis judged or determined that a malfunction due to crosstalk noise iscreated.

The error criterion generation section 10 selects the error informationfrom the error information storage unit 3, and generates an errorcriterion according to the victim receiver cell. A plurality of errorinformation may be selected. Then a combination of error criteria isgenerated by the error criterion generation section 10. For example,when the noise voltage and duration in a falling signal are selected asthe error information, the combined error criterion is generated as avalue of a function [

v=f1(

t)] as shown in FIG. 5. The error criterion generation unit 10 generatesas the error criterion the value of the function [

v=f1(

t)] which is obtained by plotting the noise voltage and the duration inthe falling signal and subjecting the value to smooth processing.Hereinafter, this error criterion is referred to as “a combinationalerror criterion of noise voltage and noise duration in a fallingsignal.” As the smooth processing, there are the nearest-neighborsmooth, the linear smooth, the cubic smooth, and the like.

The simulation executing section 15 simulates the waveform of a signalin the victim wire, especially, the waveform of a signal supplied to thevictim receiver cell for the layout pattern supplied as data by thelogic connection information input unit 1. For example, in the logiccircuit shown in FIG. 2, the simulation executing section 15 simulatesthe waveform of the clock signal supplied to the receiver cell R1,namely, the signal propagated through the wire N2.

The noise analysis section 20 detects crosstalk noise from the result ofthe simulation by the simulation executing section 15, and then measuresthe “malfunction factors” of the detected crosstalk noise. For example,the noise analysis section 20 measures the voltage (

v) and duration (

t) of the crosstalk noise generated in the falling signal propagatedthrough the wire N2 of FIG. 2 as shown in FIG. 4.

The comparison section 25 compares the “malfunction factors” of thecrosstalk noise measured by the noise analysis section 20 to the errorcriterion generated by the error criterion generation section 10. Forexample, the comparison section 25 compares a point representing thevoltage (

v) and duration (

t) of the crosstalk noise generated in the falling signal propagatedthrough the wire, which are shown in FIG. 4, to the combinational errorcriterion of noise voltage and noise duration in a falling signal shownin FIG. 5. As a result of the comparison, when the “malfunction factors”meet the error criterion, the comparison section 25 judges or determinesthat the crosstalk noise causes a malfunction of the victim receivercell, and transmits an “error signal” to the output unit 5 indicatingthat a malfunction will be created. On the contrary, when the“malfunction factors” do not meet the error criterion, the comparisonsection 25 judges or determines that the crosstalk noise does not createa malfunction of the victim receiver cell, and transmits a “normalsignal” to the output unit 5 indicating that a malfunction will not becreated.

For example, as shown in FIG. 5, it is assumed that the voltage (

v) and duration (

t) of the crosstalk noise generated in the falling signal propagatedthrough the wire are represented by a point P1. In this case, since thepoint P1 is in a region above the value of the combinational errorcriterion of the noise voltage and the noise duration in the fallingsignal, the comparison section 25 transmits the “error signal” to theoutput unit 5. On the contrary, it is assumed that the voltage (

v) and duration (

t) of the crosstalk noise are represented by a point P2 of FIG. 5. Inthis case, the point 2 is in a region below the value of thecombinational error criterion, and the comparison section 25 transmitsthe “normal signal” to the output unit 5.

A description will be given of a crosstalk noise analysis methodaccording to the first embodiment of the present invention withreference to the flowchart of FIG. 6.

(a) In step S100, the layout pattern of the logic circuit to be designedis supplied as data by the logic connection information input unit 1. Instep S105, the error criterion generation section 10 generates an errorcriterion. For example, the error criterion generation section 10generates the combinational error criterion of noise voltage and noiseduration in a falling signal.

(b) In step S110, the simulation executing section 15 simulates thewaveform of a signal in the victim wire for the layout pattern suppliedas data by the logic connection information input unit 1.

(c) In step S115, the noise analysis section 20 detects crosstalk noise.In step S120, the noise analysis section 20 measures the “malfunctionfactors” of the detected crosstalk noise.

(d) In step S125, the comparison section 25 compares the “malfunctionfactors” of the crosstalk noise measured by the noise analysis section20 to the error criterion generated by the error criterion generationsection 10. As a result of the comparison, when the “malfunctionfactors”meet the error criterion in step S130, the comparison section 25judges that the crosstalk noise creates a malfunction of the victimreceiver cell and transmits the “error signal” to the output unit 5indicating that a malfunction will be created in step S135. On thecontrary, when the “malfunction factors” do not meet the error criterionin step S130, the comparison section 25 judges that the crosstalk noisedoes not create a malfunction of the victim receiver cell and transmitsthe “normal signal” to the output unit 5 indicating that a malfunctionwill not be created in step S140.

According to the first embodiment of the present invention, theinfluence of crosstalk noise in the transition state can be accuratelyascertained. Moreover, it is possible to optimally design a logiccircuit which does not create a malfunction due to crosstalk noise.Accordingly, the circuit area and power dissipation are reduced.

(Second Embodiment)

As shown in FIG. 7, a crosstalk noise analysis system according to asecond embodiment of the present invention differs from that accordingto the first embodiment of the present invention shown in FIG. 1 in thatthe error information storage unit 3 includes a data storage section 35which stores victim receiver cell load capacity as error information.

The “victim receiver cell load capacity” indicates load capacity of thevictim receiver cell when the victim receiver cell is malfunctioningbecause of crosstalk noise. For example, when the “the noise voltage inthe falling signal (

v)” and “the noise duration in the falling signal (

t)” shown in FIG. 4 cause a malfunction of the receiver cell R1 in FIG.2, the load capacity of the receiver cell R1 is stored in the datastorage section 35 as the error information “victim receiver cell loadcapacity (C).”

In the case of selecting the noise voltage and duration in the fallingsignal, and the victim receiver cell load capacity, the error criteriongeneration section 10 generates a value of a function [C=f2(

v,

t)] shown in FIG. 8 as the error criterion. The error criteriongeneration section 10 sets as the error criterion the value of thefunction [C=f2(

v,

t)] obtained by plotting the noise voltage in the falling signal, thenoise duration in the falling signal, and the victim receiver cell loadcapacity and subjects the value to the smooth processing. Hereinafter,this error criterion is referred to as a combinational error criterionof noise voltage and noise duration in a falling signal and victimreceiver cell load capacity.

A description will be given of a crosstalk noise analysis methodaccording to the second embodiment of the present invention withreference to the flowchart of FIG. 9.

(a) In step S200, the layout pattern of the logic circuit to be designedis supplied as data by the logic connection information input unit 1. Instep S205, the error criterion generation section 10 generates thecombinational error criterion of the noise voltage and noise duration inthe falling signal and victim receiver cell load capacity.

(b) In step S210, the simulation executing section 15 simulates thewaveform of a signal in the victim wire for the layout pattern suppliedas data by the logic connection information input unit 1.

(c) In step S215, the noise analysis section 20 detects crosstalk noise.In step S220, the noise analysis section 20 measures the voltage andduration of the crosstalk noise propagated through the victim wire andthe load capacity of the victim receiver cell, which are the“malfunction factors” of the detected crosstalk noise. For example, thenoise analysis section 20 measures the voltage (

v) and duration (

t) of the crosstalk noise generated in the falling signal propagatedthrough the wire N2 in FIG. 2 and the load capacity of the receiver cellR1 in FIG. 2.

(d) In step S225, the comparison section 25 compares a pointrepresenting the voltage and duration of the crosstalk noise and theload capacity of the victim receiver cell to the combinational errorcriterion of the noise voltage and noise duration in the falling signaland victim receiver cell load capacity generated by the error criteriongeneration section 10. As a result of the comparison, when the pointrepresenting the voltage and duration of the crosstalk noise and theload capacity of the victim receiver cell as the “malfunction factors”is above the value of the combinational error criterion of the noisevoltage and noise duration in the falling signal and victim receivercell load capacity in step S227, the comparison section 25 transmits the“error signal” to the output unit 5 in step S230. On the contrary, whenthe point representing the voltage and duration of the crosstalk noiseand the load capacity of the victim receiver cell is not above the valueof the combinational error criterion of the noise voltage and noiseduration in the falling signal and victim receiver cell load capacity instep S227, the comparison section 25 transmits the “normal signal” tothe output unit 5 in step S235.

For example, it is assumed that the voltage and duration of thecrosstalk noise and the load capacity of the victim receiver cell arerepresented by a point P3 in FIG. 8. In this case, the point P3 islocated in a region above the error criterion, and the comparisonsection 25 transmits the “error signal” to the output unit 5. On thecontrary, it is assumed that the voltage and duration of the crosstalknoise and the load capacity of the victim receiver cell are representedby a point P4 in FIG. 8. In this case, the point P4 is located in aregion below the error criterion, and the comparison section 25transmits the “normal signal” to the output unit 5.

According to the second embodiment of the present invention, theinfluence of crosstalk noise in the transition state can be accuratelyascertained. Moreover, it is possible to optimally design a logiccircuit which does not create a malfunction due to crosstalk noise.Accordingly, the a large circuit design is not necessary, and thecircuit area and power dissipation are reduced.

(Third Embodiment)

As shown in FIG. 10, the crosstalk noise analysis system according to athird embodiment of the present invention differs from that according tothe first embodiment of the present invention shown in FIG. 1 in thatrising noise voltage in a constant signal is stored in a third voltagedata storage 36, rising noise duration in a constant signal is stored ina third duration data storage 37, falling noise voltage in a constantsignal is stored in a fourth voltage data storage 38, and falling noiseduration in a constant signal is stored in a fourth duration datastorage 39 as the error information, respectively. Moreover, thecrosstalk noise analysis system according to the third embodiment of thepresent invention differs from that according to the first embodiment ofthe present invention shown in FIG. 1 in that it includes a net analysissection 6.

The “rising noise voltage in a constant signal” is voltage of crosstalknoise generated in a constant signal propagated through a wire andcauses the victim receiver cell to misidentify the crosstalk noise asthe rising signal. For example, as shown in FIG. 11, with the rising ofa signal W1 in the wire N1 of FIG. 2 at a time T5, crosstalk noise witha voltage (

v) is generated in a constant low signal W2 propagated through the wireN2 of FIG. 2 and causes a malfunction of the receiver cell R1 of FIG. 2as a rising signal. In this case, the rising noise voltage in theconstant signal (

v) is stored as error information in the third voltage data storage 36.

The “rising noise duration in a constant signal” is duration ofcrosstalk noise generated in the constant signal propagated through awire and causes the victim receiver cell to misidentify the crosstalknoise as a rising signal. For example, as shown in FIG. 11, with therising of the signal W1 in the wire N1 at the time T5, crosstalk noisewith a duration (

t=T6−T5) is generated in the wire N2 when the signal W2 is in the staticstate and causes a malfunction of the receiver cell R1 as a risingsignal. In this case, the rising noise duration in the constant signal (

t) is stored as error information in the third duration data storage 37.

The “falling noise voltage in a constant signal” is voltage of crosstalknoise generated in a constant signal propagated through a wire andcauses the victim receiver cell to misidentify the crosstalk noise as afalling signal. For example, as shown in FIG. 12, with the falling of asignal W1 in the wire N1 at a time T7, crosstalk noise with a voltage (

v=V8−V7) is generated in a constant high signal W2 propagated throughthe wire N2 and causes a malfunction of the receiver cell R1 as afalling signal. In this case, the falling noise voltage in the constantsignal (

v) is stored as error information in the fourth voltage data storage 38.

The “falling noise duration in a constant signal” is duration ofcrosstalk noise generated in the constant signal propagated through awire and causes the victim receiver cell to misidentify the crosstalknoise as the falling signal. For example, as shown in FIG. 12, with thefalling of the signal W1 in the wire N1 at the time T7, crosstalk noisewith a duration (

t=T8−T7) is generated in the wire N2 when the signal W2 is in the staticstate and causes a malfunction of the receiver cell R1 as a fallingsignal. In this case, the falling noise duration in a constant signal (

t) is stored as error information in the fourth duration data storage39.

The net analysis section 6 distinguishes, in the layout pattern suppliedas data by the logic connection information input unit 1, a net throughwhich the clock signal is propagated from a net through which thegeneral signal other than the clock signal is propagated. For example,in FIG. 2, the wire N2 through which the clock signal is propagated isdistinguished from the wire N1 through which the general signal ispropagated. For the net with the general signal propagated therethrough,the net analysis section 6 orders the error criterion generation section10 to eliminate the error criterion relating to the malfunction factorscaused in the rising and falling signals propagated through the victimwire.

In the case of selecting the rising noise voltage and duration in theconstant signal from the error information storage unit 3, the errorcriterion generation section 10 generates a value of a function [

v=f3(

t)] shown in FIG. 13 as the error criterion. The error criteriongeneration section 10 sets, as the error criterion, the value of thefunction [

v=f3(

t)] obtained by plotting the rising noise voltage in the signal andrising noise duration in the signal and subjecting the value to thesmooth processing. Hereinafter, this error criterion is referred to as acombinational error criterion of rising noise voltage and duration in aconstant signal.

For the net having the general signal propagated therethrough, the errorcriterion generation section 10 does not generate the error criterionrelating to the malfunction factors generated in the rising and fallingsignals propagated through the victim wire. For example, for the nethaving the general signal propagated therethrough, the combinationalerror criterion of noise voltage and noise duration in a falling signalis not generated, and only the combinational error criterion of risingnoise voltage and rising noise duration in a constant signal isgenerated. In this case, the influence of the crosstalk noise on therising or falling signal is eliminated by adjusting a delay of thegeneral signal.

A description will be given of a crosstalk noise analysis methodaccording to the third embodiment of the present invention withreference to a flowchart of FIG. 14.

(a) In step S300, the layout pattern of the logic circuit to be designedis supplied as data by the logic connection information input unit 1. Instep S305, the net analysis section 6 distinguishes the net with theclock signal propagated therethrough from the net with the generalsignal propagated therethrough in the layout pattern. In step S310, asfor the net with the general signal propagated therethrough, the netanalysis section 6 orders the error criterion generation section 10 toeliminate the error criterion relating to the malfunction factorsgenerated in the rising and falling signals. In step S315, the errorcriterion generation section 10 generates an error criterion. At thistime, the eliminated error criterion is not generated.

(b) In step S320, the simulation executing section 15 simulates thewaveforms of the signals in the transition and static states for thelayout pattern.

(c) In step S325, the noise analysis section 20 detects crosstalk noise.In step S330, the noise analysis section 20 measures the “malfunctionfactors” of the detected crosstalk noise. For example, the noiseanalysis section 20 measures the voltage (

v) and duration (

t) of the crosstalk noise generated in the constant signal and thevoltage (

v) and duration (

t) of the crosstalk noise generated in the falling signal.

(d) In step S335, the comparison section 25 compares the “malfunctionfactors” of the crosstalk noise measured by the noise analysis section20 to the error criterion generated by the error criterion generationsection 10.

For example, the comparison section 25 compares a point representing thevoltage (

v) and duration (

t) of the crosstalk noise to the combinational error criterion of therising noise voltage and the noise duration in the constant signalgenerated by the error criterion generation section 10. As for the clocksignal, the comparison section 25 further compares a point representingthe voltage and duration of the crosstalk noise generated in the fallingsignal to the combinational error criterion of the noise voltage and thenoise duration in the falling signal.

(e) As a result of the comparison, when the “malfunction factors” meetthe error criterion in step S340, the comparison section 25 judges thatthe crosstalk noise creates a malfunction of the victim receiver celland transmits the “error signal” to the output unit 5 indicating that amalfunction will be created in step S345. On the contrary, when the“malfunction factors” do not meet the error criterion in step S340, thecomparison section 25 judges that the crosstalk noise does not create amalfunction of the victim receiver cell and transmits the “normalsignal” to the output unit 5 indicating that a malfunction is not to becaused in step S350.

For example, the voltage (

v) and duration (

t) of the crosstalk noise generated in the constant signal arerepresented by a point P5 in FIG. 13. In this case, since the point P5is located in a region above the error criterion, the comparison section25 transmits the “error signal” to the output unit 5. On the contrary,as for the net with the general signal propagated therethrough, thevoltage (

v) and duration (

t) of the crosstalk noise generated in the constant signal arerepresented by a point P6 in FIG. 13. In this case, since the point P6is located in a region below the combinational error criterion of thenoise voltage and the noise duration in the constant signal, thecomparison section 25 transmits the “normal signal” to the output unit5.

According to the third embodiment of the present invention, theselection of the error criterion to be used for each net allowsreduction of pseudo errors in the crosstalk noise analysis, thusspeeding up the optimal design process of the logic circuit.

(Fourth Embodiment)

As shown in FIG. 15, a crosstalk noise analysis system according to afourth embodiment of the present invention differs from that accordingto the first embodiment of the present invention shown in FIG. 1 in thatthe rising noise voltage in the constant signal, the rising noiseduration in the constant signal, the falling noise voltage in theconstant signal, and the falling noise duration in the constant signalare stored as the error information in the data storage 36 to 39,respectively. Moreover, the crosstalk noise analysis system according tothe fourth embodiment of the present invention differs from thataccording to the first embodiment of the present invention shown in FIG.1 in that it includes an error criterion analysis section 7.

The error criterion analysis section 7 analyzes a plurality of errorcriteria generated by the error criterion generation section 10. Whenany one of the plurality of error criteria is included by another errorcriterion, the error criterion analysis section 7 orders the comparisonsection 25 to eliminate the included error criterion. The comparisonsection 25 eliminates that error criterion. For example, in FIG. 16,when the noise voltage and the noise duration in the falling signal isabove the combinational error criterion, a point representing thevoltage and duration of crosstalk noise is always above thecombinational error criterion of the rising noise voltage and noiseduration in the constant signal. In other words, the combinational errorcriterion of the noise voltage and noise duration in the falling signalis included by the combinational error criterion of the rising noisevoltage and noise duration in the constant signal. Accordingly, in thiscase, the combinational error criterion of the noise voltage and noiseduration in the falling signal is eliminated from the error criteria.

A description will be given of a crosstalk noise analysis methodaccording to the fourth embodiment of the present invention withreference to a flowchart of FIG. 17.

(a) In step S400, the layout pattern of the logic circuit to be designedis supplied as data by the logic connection information input unit 1. Instep S405, the error criterion generation section 10 generates the errorcriteria. For example, the error criterion generation section 10generates the combinational error criterion of the noise voltage andnoise duration in the falling signal and the combinational errorcriterion of the rising noise voltage and noise duration in the constantsignal from the error information storage unit 3. In step S410, theerror criterion analysis section 7 analyzes whether each error criterionis included in another error criterion. For example, the error criterionanalysis section 7 analyzes whether one of the error criteria “the noisevoltage and noise duration in the falling signal” and “the rising noisevoltage and noise duration in the constant signal” is included in theother. When it is analyzed that an error criterion is included inanother error criterion in step S415, the error criterion analysissection 7 orders the comparison section 25 to eliminate the includederror criterion in step S420, and the procedure proceeds to step S425.

(b) In step S425, the simulation executing section 15 simulates thewaveform of the signal propagated through the victim wire for the layoutpattern.

(c) In step S430, the noise analysis section 20 detects crosstalk noise.In step S435, the noise analysis section 20 measures the “malfunctionfactors” of the detected crosstalk noise. For example, the noiseanalysis section 20 measures the voltage (

v) and duration (

t) of the crosstalk noise generated in the constant signal and thevoltage (

v) and duration (

t) of the crosstalk noise generated in the falling signal.

(d) In step S440, the comparison section 25 compares the “malfunctionfactors” of the crosstalk noise measured by the noise analysis section20 to the error criterion generated by the error criterion generationsection 10. In this case, the comparison section 25 does not use theeliminated error criterion. For example, in the case where thecombinational error criterion of the noise voltage and noise duration inthe falling signal is included by the combinational error criterion ofthe rising noise voltage and noise duration in the constant signal asshown in FIG. 16, the comparison section 25 does not compare the voltage(

v) and duration (

t) of the crosstalk noise generated in the falling signal to thecombinational error criterion of the noise voltage and noise duration inthe falling signal generated by the error criterion generation section10.

(e) As a result of the comparison, when the “malfunction factors” meetthe error criterion in step S445, the comparison section 25 judges thatthe crosstalk noise creates a malfunction of the victim receiver celland transmits the “error signal” to the output unit 5 indicating that amalfunction will be created in step S450. On the contrary, when the“malfunction factors” do not meet the error criterion in step S445, thecomparison section 25 judges that the crosstalk noise does not cause amalfunction of the victim receiver cell and transmits the “normalsignal” to the output unit 5 indicating that a malfunction will not becreated in a step S445.

According to the fourth embodiment of the present invention, theselection of the error criterion for each net allows reduction of thepseudo-errors in the crosstalk noise analysis, thus speeding up theoptimal design process of the logic circuit.

(Fifth Embodiment)

As shown in FIG. 18, a crosstalk noise analysis system according to thefifth embodiment of the present invention differs from that according tothe first embodiment of the present invention shown in FIG. 1 in thatthe rising noise voltage in the constant signal, the rising noiseduration in the constant signal, the falling noise voltage in theconstant signal, and the falling noise duration in the constant signalare stored as the error information in the data storage 36 to 39,respectively. Moreover, as shown in FIG. 18, the crosstalk noiseanalysis system according to the fifth embodiment of the presentinvention differs from that according to the first embodiment of thepresent invention shown in FIG. 1 in that it includes a timinginformation input unit 9 and a logic connection information analysissection 8.

The timing information input unit 9 transmits timing information of theclock and general signals which are supplied to the logic circuit to bedesigned. The simulation executing section 15 simulates the waveform ofthe signal propagated through the victim wire using the timinginformation supplied by the timing information input unit 9. Thissimulation allows the waveform of the signal to be accuratelyascertained.

The logic connection information analysis section 8 analyzes the logiccircuit supplied by the logic connection information input unit 1 andselects a signal which causes the victim receiver cell to operate fromone of a rising signal and a falling signal propagated through a victimwire. For example, as shown in FIG. 19, a logic circuit comprises areceiver cell R2, a driver D4 transmitting a clock signal through a wireN4, and a driver D3 transmitting the clock signal through a wire N3. Thereceiver cell R2 operates on the rising clock signal. Specifically, therising signal propagated through the wire N4 causes operation of thereceiver cell R2. Accordingly, the rising signal is selected by thelogic connection information analysis section 8 for the wire N4.Meanwhile, since the driver D4 is an inverter, the falling signalpropagated through the wire N3 causes operation of the receiver cell R2.Accordingly, the falling signal is selected by the logic connectioninformation analysis section 8 for the wire N3. In such a manner, thelogic is traced backward from the victim receiver cell. Alternatively,the logic may be traced from the root of a clock tree. The logicconnection information analysis section 8 orders the error criteriongeneration section 10 to eliminate the error criterion relating to themalfunction factors created the signal that is different from theselected signal. In other words, in the logic circuit shown in FIG. 19,the error criterion relating to the malfunction factors created thefalling signal is eliminated for the wire N4, and the error criterionconcerning the malfunction factors created the rising signal iseliminated for the wire N3.

The error criterion generation section 10 does not generate the errorcriterion to be eliminated. For example, for the wire N4, thecombinational error criterion of the noise voltage and noise duration inthe falling signal and the combinational error criterion of the risingnoise voltage and noise duration in the constant signal related to thenoise which does not create the malfunction of the victim receiver cellR2 are not generated.

A computer implemented method for a crosstalk noise analysis accordingto the fifth embodiment of the present invention will be described withreference to a flowchart of FIG. 20.

(a) In step S500, the layout pattern of the logic circuit to be designedis supplied as data by the logic connection information input unit 1. Instep S505, the logic connection information analysis section 8 analyzesthe supplied logic circuit and selects a signal that causes the victimreceiver cell to operate from among the falling and rising signalspropagated through the victim wire. In step S510, the logic connectioninformation analysis section 8 orders the error criterion generationsection 10 to eliminate the error criterion related to the malfunctionfactors relating to the signal that is different from the selectedsignal. In step S515, the error criterion generation section 10generates the error criteria. At this time, the error criteriongeneration section 10 does not generate the error criterion which is tobe eliminated.

(b) In step S520, the timing information input unit 9 transmits thetiming information of the previously known clock and general signals. Instep S525, the simulation executing section 15 simulates the waveformsof the signals in the transition and static states using the timinginformation supplied by the timing information input unit 9.

(c) In step S530, the noise analysis section 20 detects crosstalk noise.In step S535, the noise analysis section 20 measures the “malfunctionfactors” of the detected crosstalk noise.

(d) In step S540, the comparison section 25 compares the “malfunctionfactors” of the crosstalk noise measured by the noise analysis section20 to the error criterion generated by the error criterion generationsection 10.

(e) As a result of the comparison, when the “malfunction factors” meetthe error criterion in step S545, the comparison section 25 judges thatthe crosstalk noise creates a malfunction of the victim receiver celland transmits the “error signal” to the output unit 5 indicating that amalfunction will be created in step S550. On the contrary, when the“malfunction factors” do not meet the error criterion in step S545, thecomparison section 25 judges that the crosstalk noise does not cause amalfunction of the victim receiver cell and transmits the “normalsignal” to the output unit 5 indicating that a malfunction will not becreated in step S555.

According to the fifth embodiment of the present invention, theselection of the error criterion for each net allows reduction of thepseudo-errors in the crosstalk noise analysis, thus speeding up theoptimal design process of the logic circuit.

Various modifications will become possible for those skilled in the artafter receiving the teachings of the present disclosure withoutdeparting from the scope thereof.

1. A system for analyzing noise comprising: an error information storageunit storing threshold values of malfunction factors that create amalfunction of a victim receiver cell due to a noise; an error criteriongeneration section configured to select the threshold values from theerror information storage unit, and to generate an error criterionaccording to the victim receiver cell by plotting the threshold valuesand subjecting the threshold values to smooth processing; a noiseanalysis section configured to measure the malfunction factors; acomparison section configured to compare the measured malfunctionfactors to the error criterion, and to judge whether the noise willcreate a malfunction of the victim receiver cell when the malfunctionfactors meet the error criterion; and a net analysis section configuredto distinguish a net through which a clock signal is propagated fromanother net through which a general signal other than the clock signalis propagated and to order the error criterion generation section toeliminate the error criterion relating to the malfunction factorsgenerated in rising and falling signals propagated through the netthrough which the general signal is propagated.
 2. The system of claim1, further comprising an error criterion analysis section configured toanalyze a plurality of error criteria, and to order to eliminate anerror criterion from among a plurality of error criteria, which isincluded in another error criterion from among the plurality of errorcriteria.
 3. The system of claim 2, further comprising: a logicconnection information input unit configured to transmit data to bedesigned for a layout pattern of a logic circuit; and a simulationexecuting section configured to simulate waveforms of the noise and theclock signal in the logic circuit.
 4. The system of claim 1, furthercomprising a logic connection information analysis section configured toselect a signal which causes the victim receiver cell to operate fromamong the falling and rising signals and to order the error criteriongeneration section to eliminate the error criterion relating to themalfunction factors created in another signal that is different from thesignal selected from among the falling and rising signals.
 5. The systemof claim 4, further comprising: a logic connection information inputunit configured to transmit data to be designed for a layout pattern ofa logic circuit; and a simulation executing section configured tosimulate waveforms of the noise and the clock signal in the logiccircuit.
 6. The system of claim 1, further comprising: a logicconnection information input unit configured to transmit data to bedesigned for a layout pattern of a logic circuit; and a simulationexecuting section configured to simulate waveforms of the noise and theclock signal in the logic circuit.
 7. A computer implemented method foranalyzing noise comprising: generating an error criterion according to avictim receiver cell, by plotting threshold values of malfunctionfactors that create a malfunction of the victim receiver cell due to anoise and subjecting the threshold values to smooth processing;measuring the malfunction factors; comparing the measured malfunctionfactors to the error criterion; judging whether the noise creates amalfunction of the victim receiver cell when the malfunction factorsmeet the error criterion; distinguishing a net through which a clocksignal is propagated from another net through which a general signalother than the clock signal is propagated; and eliminating the errorcriterion relating to the malfunction factors created in rising andfalling signals propagated through the net through which the generalsignal is propagated.
 8. The method of claim 7, further comprisingordering elimination of an error criterion from among a plurality oferror criteria, which is included in another error criterion from amongthe plurality of error criteria.
 9. The method of claim 8, furthercomprising: transmitting data of a layout pattern of a logic circuit tobe designed; and simulating waveforms of the noise and the clock signalin the logic circuit.
 10. The method of claim 7, further comprising:selecting a signal that causes the victim receiver cell to operate fromamong the falling and rising signals; and eliminating the errorcriterion relating to the malfunction factors generated in anothersignal that is different from the selected signal from among the fallingand rising signals.
 11. The method of claim 10, further comprising:transmitting data of a layout pattern of a logic circuit to be designed;and simulating waveforms of the noise and the clock signal in the logiccircuit.
 12. The method of claim 7, further comprising: transmittingdata of a layout pattern of a logic circuit to be designed; andsimulating waveforms of the noise and the clock signal in the logiccircuit.
 13. A system for analyzing noise comprising: an errorinformation storage unit storing threshold values of malfunction factorsthat create a malfunction of a victim receiver cell due to a noise; anerror criterion generation section configured to select the thresholdvalues from the error information storage unit, and to generate an errorcriterion according to the victim receiver cell by plotting thethreshold values and subjecting the threshold values to smoothprocessing; a noise analysis section configured to measure themalfunction factors; a comparison section configured to compare themeasured malfunction factors to the error criterion, and to judgewhether the noise will create a malfunction of the victim receiver cellwhen the malfunction factors meet the error criterion; and a netanalysis section configured to distinguish a net through which a clocksignal is propagated from another net through which a general signalother than the clock signal is propagated and to order the errorcriterion generation section to eliminate the error criterion relatingto the malfunction factors generated in rising and falling signalspropagated through the net through which the general signal ispropagated, wherein the error information storage unit stores at leastone of a noise voltage in the rising signal transmitted to the victimreceiver cell, a noise duration in the rising signal transmitted to thevictim receiver cell, a noise voltage in the falling signal transmittedto the victim receiver cell, a noise duration in the falling signaltransmitted to the victim receiver cell, and the victim receiver cellload capacity as the threshold values.
 14. The system of claim 13,further comprising an error criterion analysis section configured toanalyze a plurality of error criteria, and to order to eliminate anerror criterion from among a plurality of error criteria, which isincluded in another error criterion from among the plurality of errorcriteria.
 15. The system of claim 13, further comprising a logicconnection information analysis section configured to select a signalwhich causes the victim receiver cell to operate from among the fallingand rising signals and to order the error criterion generation sectionto eliminate the error criterion relating to the malfunction factorscreated in another signal that is different from the signal selectedfrom among the falling and rising signals.
 16. The system of claim 13,further comprising: a logic connection information input unit configuredto transmit data to be designed for a layout pattern of a logic circuit;and a simulation executing section configured to simulate waveforms ofthe noise and the clock signal in the logic circuit.